Your comments

Please send the debug log file to support@textasticapp.com and I'll have a look.
Textastic supports TextExpander snippet expansion. Did you have a look at this app? http://www.smilesoftware.com/TextExpander/touch/index.html
Did you choose "ASP - VB" as Syntax Definition in the File Information popover? 

I just had a look at the syntax definition file and single quotes are correctly set as the start character for single line comments.

Are you using Textastic 2.1?
No, I don't have any plans for an Android version of Textastic.
Unfortunately, iOS doesn't give direct access to keyboard keys. For example, it's not possible to detect the current state of the Ctrl, Cmd or Shift key.

iOS just sends commands to text views like "insert character" when pressing a keyboard or "delete backward" when pressing backspace or "move one character left/right" when pressing the arrow keys or "move one word left/right" when ctrl is pressed in addition to an arrow key.

Some time ago I read that an app called "Essay" supports shortcuts. See http://www.essayapp.com/about.html

"iOS does not provide full access to external keyboards. But Essay wanted to make shortcuts available to the writers to assist an optimal workflow without the need to lift the hands from the keyboard. Therefore we feature a special command mode. It works like this: you enter ALT + SPACE to bring Essay into a Waiting for Command Mode. Then press one of the following keys or any other and the command will be executed and you can from then on continue to write as usual. "


So this would be a possible workaround.

That's pretty much the standard behaviour of iOS text controls.

If you just want to browse your code, I recommend enabling the read-only mode in the app's settings. This prevents the keyboard from coming up.

I'm reading all your comments but I'm still undecided.

Implementing a full-fledged graphical version control client like Versions (Subversion) or Tower (Git) on iPad would require a huge amount of work.
For the moment, you can enter a very high wrap column value in Textastic's settings.
Exactly (see my comment above). I'm going to change the behavior of Textastic accordingly.